ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



879 



4000 it remains inert and benumbed. Wlien its normal pressure 

 returns it recommences moving, unless the pressure lias been pro- 

 longed and its tissues are soaked. This seems to show that the eifect 

 is a compression of the nervous system. 



Westien's apparatus for comparing symmetrical parts of the 

 webs of the right and left feet of a frog.* — The apparatus of 

 Herr H. Westien (fig. 210) consists of a glass plate holder C, the 

 stand P, and the Microscope A (upper part omitted). The ring m, 

 movable on the upright n, is fastened by the screw lo and carries the 

 bar 0, to which the clamp S is attached. The glass plate K is clamped 

 into this, and on it the frog is laid, and its extremities and toes fixed 

 with threads which are fastened in holes bored in the glass plate. 



Fig. 210. 



The plate K rests on the glass-plate G, on which it can be easily and 

 quickly pushed in a horizontal plane up to the clamps c c which are 

 fastened on the upper border of the glass plate G. By proper adjust- 

 ment of the glass plate K on a certain spot, e. g. a small artery of the 

 left foot, the corresponding spot of the right foot can be placed in the 

 field by pushing the plate up to the clamp c. The apparatus for pro- 

 ducing stimuli a is attached to the glass plate K by the clamp K. 



Apparatus for Determining the Specific Gravity of Minute 

 Objects under the Microscope. f — Prof. W. J. Sollas found the diffi- 

 culty of determining the specific gravity of calcareous sponge spicules 

 by the method of weighing insuperable, as they are so small and 

 so difiicult to free completely from air, even with an air-pump. 

 Sonstadt's solution appeared to oficr the best chance of success ; but 

 here again the small size of the spicules was a difficulty. This, 

 however, was overcome by adapting the Sonstadt method for use with 

 the Microscope. 



An ordinary collecting tube (fig. 211, T), about 2 in. long and 

 3/8 in. in diameter, was cemented with plenty of Canada balsam to 

 a glass slide G. The object of using excess of balsam -was to destroy 



• Zeitschr. f. InBtnimcntf^nkunfle, v. (188.'5)p. 198 (1 fipf.) 



t Scieiilif. Proc. U. Dii))liii Soc, IHHf., i>|). :'.74-f)2 (7 fig.s. niid 1 pi.). 



